In the existing bendable mechanical structures, controllable bending motions are realized basically by two mutually hinged rigid or flexible links through relative rotation at hinged joints. When serial connection of a plurality of independent bending motions is realized through this kind of structure, due to the difficulty in transmission arrangement, generally a drive unit (such as a motor or a hydraulic ejector rod and the like) needs to be installed at each hinged joint and thus distal driving units become the load of proximal drive units, such that the realized structure with this function becomes relatively complex and the size is relatively larger.
In application such as medical surgery or industrial intra-cavity inspection, an extremely small peripheral size is needed for constructing a multi-DOF (degree-of-freedom) and multi-bending-function instrument especially for MIS (minimally invasive surgery) or industrial intra-cavity inspection. Obviously, the previously described solution of realizing the serially connected mechanical structure through a mutual hinged manner has many defects which are difficult to overcome.